Prepolymers with dangling polysiloxane-containing polymer chains

ABSTRACT

The invention provide a new class of silicone-containing prepolymers containing dangling polysiloxane-containing polymer chains. This class of silicone-containing prepolymer is capable of being actinically crosslinked to form a silicone hydrogel material with a relatively high oxygen permeability, a reduced elastic modulus, and a relatively high ion permeability. The present invention is also related to silicone hydrogel contact lenses made from this class of silicone-containing prepolymers and to methods for making the silicone hydrogel contact lenses.

This application is a divisional application of application Ser. No.12/077,772, filed Mar. 21, 2008, now U.S. Pat. No. 8,071,658 whichclaims the benefit under 35 USC §119 (e) of U.S. provisional applicationNo. 60/896,325 filed Mar. 22, 2007, incorporated herein by reference inits entirety.

The present invention is related to a class of silicone-containingprepolymers with dangling polysiloxane-containing polymer chains anduses thereof. In particular, the present invention is related tosilicone hydrogel contact lenses made from this class ofsilicone-containing prepolymers.

BACKGROUND

In recent years, soft silicone hydrogel contact lenses has becomepopular because of their high oxygen permeability and comfort. “Soft”contact lenses conform closely to the shape of the eye, so oxygen cannoteasily circumvent the lens. Soft contact lenses must allow oxygen fromthe surrounding air (i.e., oxygen) to reach the cornea because thecornea does not receive oxygen from the blood supply like other tissue.If sufficient oxygen does not reach the cornea, corneal swelling occurs.Extended periods of oxygen deprivation cause the undesirable growth ofblood vessels in the cornea. By having high oxygen permeability, asilicone hydrogel contact lens allows sufficient oxygen to permeatethrough the lens to the cornea and to have minimal adverse effects oncorneal health.

However, all commercially available silicone hydrogel contact lenses areproduced according to a conventional cast molding technique involvinguse of disposable plastic molds and a mixture of monomers and/ormacromers. There are several disadvantages with such conventionalcast-molding technique. For example, a traditional cast-moldingmanufacturing process must include lens extraction in whichunpolymerized monomers must be removed from the lenses by using anorganic solvent. Such lens extraction increases the production cost anddecreases the production efficiency. In addition, disposable plasticmolds inherently have unavoidable dimensional variations, because,during injection-molding of plastic molds, fluctuations in thedimensions of molds can occur as a result of fluctuations in theproduction process (temperatures, pressures, material properties), andalso because the resultant molds may undergo non-uniform shrinkage afterthe injection molding. These dimensional changes in the mold may lead tofluctuations in the parameters of contact lenses to be produced (peakrefractive index, diameter, basic curve, central thickness etc.) and toa low fidelity in duplicating complex lens design.

The above described disadvantages encountered in a conventionalcast-molding technique can be overcome by using the so-calledLightstream Technology™ (CIBA Vision), which involves (1) a lens-formingcomposition being substantially free of monomers and comprising asubstantially purified prepolymer with ethylenically-unsaturated groups,(2) reusable molds produced in high precision, and (3) curing under aspatial limitation of actinic radiation (e.g., UV), as described in U.S.Pat. Nos. 5,508,317, 5,583,463, 5,789,464, and 5,849,810. Lenses can beproduced at relatively lower cost according to the LightstreamTechnology™ to have high consistency and high fidelity to the originallens design.

In order to fully utilize the Lightstream Technology™ to make siliconehydrogel contact lenses, there is still a need for newactinically-crosslinkable prepolymers suitable for making siliconehydrogel contact lenses with desired mechanical strength and desiredphysical properties according to the Lightstream Technology™.

SUMMARY OF THE INVENTION

The present invention, in one aspect, provides an actinicallycrosslinkable prepolymer. The prepolymer of the invention comprises: (1)dangling polysiloxane units derived from one or more monoethylenicallyfunctionalized polysiloxane-containing monomers and/or one or moremonoethylenically-functionalized polysiloxane-containing macromers,wherein the dangling polysiloxane units is free of ethylenicallyunsaturated group; (2) hydrophilic units derived from one or morehydrophilic vinylic monomers; (3) crosslinking units derived from atleast one polysiloxane-containing crosslinker and/or at least onesilicone-free crosslinker; and (4) optionally hydrophobic units derivedfrom at least one hydrophobic vinylic monomer, wherein the prepolymercomprises multiple ethylenically unsaturated groups and is capable ofbeing actinically crosslinked, in the absence of one or more monomers,to form a silicone hydrogel material.

In another aspect, the invention provides a soft contact lens. The softcontact lens of the invention comprises: a silicone hydrogel materialthat is obtained by curing a lens-forming material in a mold, whereinthe lens-forming material comprises an actinically crosslinkableprepolymer and is substantially free of vinylic monomers andcrosslinking agent with molecular weight of less than 1500 Daltons,wherein the prepolymer comprises (1) dangling polysiloxane units derivedfrom one or more monoethylenically functionalizedpolysiloxane-containing monomers and/or one or moremonoethylenically-functionalized polysiloxane-containing macromers,wherein the dangling polysiloxane units is free of ethylenicallyunsaturated groups; (2) hydrophilic units derived from one or morehydrophilic vinylic monomers; (3) crosslinking units derived from atleast one polysiloxane-containing crosslinker and/or at least onesilicone-free crosslinker; (4) multiple ethylenically unsaturatedgroups; and (5) optionally hydrophobic units derived from at least onehydrophobic vinylic monomer.

In a further aspect, the invention provides a method for producing softcontact lenses. The method comprises the steps of: providing a mold formaking a soft contact lens, wherein the mold has a first mold half witha first molding surface defining the anterior surface of a contact lensand a second mold half with a second molding surface defining theposterior surface of the contact lens, wherein said first and secondmold halves are configured to receive each other such that a cavity isformed between said first and second molding surfaces; introduce alens-forming material into the cavity, wherein the lens-forming materialcomprises one or more actinically crosslinkable prepolymers and issubstantially free of vinylic monomer and/or crosslinking agent withmolecular weight less than 1500 Daltons, wherein each of said one ormore prepolymers comprises (1) dangling polysiloxane units derived fromone or more monoethylenically functionalized polysiloxane-containingmonomers and/or one or more monoethylenically-functionalizedpolysiloxane-containing macromers, wherein the dangling polysiloxaneunits is free of ethylenically unsaturated groups, (2) hydrophilic unitsderived from one or more hydrophilic vinylic monomers, (3) crosslinkingunits derived from at least one polysiloxane-containing crosslinkerand/or at least one silicone-free crosslinker, (4) multipleethylenically unsaturated groups, and (5) optionally hydrophobic unitsderived from at least one hydrophobic vinylic monomer; and actinicallyirradiating the composition in the mold to crosslink said one or morecrosslinkable prepolymers to form the contact lens.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Generally, the nomenclatureused herein and the laboratory procedures are well known and commonlyemployed in the art. Conventional methods are used for these procedures,such as those provided in the art and various general references. Wherea term is provided in the singular, the inventors also contemplate theplural of that term. The nomenclature used herein and the laboratoryprocedures described below are those well known and commonly employed inthe art.

An “ophthalmic device”, as used herein, refers to a contact lens (hardor soft), an intraocular lens, a corneal onlay, other ophthalmic devices(e.g., stents, glaucoma shunt, or the like) used on or about the eye orocular vicinity.

“Contact Lens” refers to a structure that can be placed on or within awearer's eye. A contact lens can correct, improve, or alter a user'seyesight, but that need not be the case. A contact lens can be of anyappropriate material known in the art or later developed, and can be asoft lens, a hard lens, or a hybrid lens. A “silicone hydrogel contactlens” refers to a contact lens comprising a silicone hydrogel material.

A “hydrogel” or “hydrogel material” refers to a polymeric material whichcan absorb at least 10 percent by weight of water when it is fullyhydrated.

A “silicone hydrogel” refers to a silicone-containing hydrogel obtainedby copolymerization of a polymerizable composition comprising at leastone silicone-containing monomer or at least one silicone-containingmacromer or at least one crosslinkable silicone-containing prepolymer.

“Hydrophilic,” as used herein, describes a material or portion thereofthat will more readily associate with water than with lipids.

A “monomer” means a low molecular weight compound that can bepolymerized. Low molecular weight typically means average molecularweights less than 700 Daltons.

A “macromer” refers to a medium and high molecular weight compound whichcan be polymerized and/or crosslinked. Medium and high molecular weighttypically means average molecular weights greater than 700 Daltons.

A “polysiloxane” refers to a moiety of

in which R₁ and R₂ are independently a monovalent C₁-C₁₀ alkyl, C₁-C₁₀ether, C₁-C₁₀ fluoroalkyl, C₁-C₁₀ fluoroether, or C₆-C₁₈ aryl radical,which may comprise hydroxy group, primary, secondary, or tertiary aminegroup, carboxy group, or carboxylic acid; n is an integer of 4 orhigher.

A “vinylic monomer”, as used herein, refers to a monomer that has onlyone ethylenically unsaturated group and can be polymerized actinicallyor thermally.

The term “olefinically unsaturated group” or “ethylenically unsaturatedgroup” is employed herein in a broad sense and is intended to encompassany groups containing a >C═C< group. Exemplary ethylenically unsaturatedgroups include without limitation acryloyl, methacryloyl, allyl, vinyl,styrenyl, or other C═C containing groups.

As used herein, “actinically” in reference to curing, crosslinking orpolymerizing of a polymerizable composition, a prepolymer or a materialmeans that the curing (e.g., crosslinked and/or polymerized) isperformed by actinic irradiation, such as, for example, UV irradiation,ionized radiation (e.g. gamma ray or X-ray irradiation), microwaveirradiation, and the like. Thermal curing or actinic curing methods arewell-known to a person skilled in the art.

The term “fluid” as used herein indicates that a material is capable offlowing like a liquid.

A “hydrophilic vinylic monomer” refers to a vinylic monomer which can bepolymerized to form a polymer that is water-soluble or can absorb atleast 10 percent by weight of water when fully hydrated.

A “hydrophobic vinylic monomer”, as used herein, refers to a vinylicmonomer which is polymerized to form a polymer that is insoluble inwater and can absorb less than 10 percent by weight water when fullyhydrated.

A “prepolymer” refers to a starting polymer which contains multipleethylenically unsaturated groups and can be cured (e.g., crosslinked)actinically to obtain a crosslinked polymer (i.e., final polymer) havinga molecular weight much higher than the starting polymer.

“Multiple” ethylenically unsaturated groups means at least two,preferably at least three ethylenically unsaturated groups.

A “silicone-containing prepolymer” refers to a prepolymer which containssilicone and ethylenically unsaturated groups can be crosslinkedactinically to obtain a crosslinked polymer having a molecular weightmuch higher than the starting polymer.

“Molecular weight” of a polymeric material (including monomeric ormacromeric materials), as used herein, refers to the number-averagemolecular weight unless otherwise specifically noted or unless testingconditions indicate otherwise.

“Polymer” means a material formed by polymerizing one or more monomers.

As used herein, the term “ethylenically functionalize” in reference to acopolymer is intended to describe that one or more ethylenicallyunsaturated groups have been covalently attached to a copolymer throughthe pendant or terminal functional groups of the copolymer according toa coupling process. A “monoethylenically functionalized” in reference toa compound means that the compound has been modified chemically tocontain one single ethylenically unsaturated group. A “diethylenicallyfunctionalized” a compound means that the compound has been modifiedchemically to contain only two ethylenically unsaturated groups.

The term “dangling polysiloxane units” of a prepolymer is intended torefer to the units each comprise a polysiloxane-containing polymer chainwhich is anchored to the main chain of the prepolymer through one singlecovalent linkage (preferably at one of the ends of thepolysiloxane-containing polymer chain).

A “photoinitiator” refers to a chemical that initiates radicalcrosslinking/polymerizing reaction by the use of light. Suitablephotoinitiators include, without limitation, benzoin methyl ether,diethoxyacetophenone, a benzoylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, Darocure® types, and Irgacure® types, preferablyDarocure® 1173, and Irgacure® 2959.

A “thermal initiator” refers to a chemical that initiates radicalcrosslinking/polymerizing reaction by the use of heat energy. Examplesof suitable thermal initiators include, but are not limited to,2,2′-azobis(2,4-dimethylpentanenitrile),2,2′-azobis(2-methylpropanenitrile), 2,2′-azobis(2-methylbutanenitrile),peroxides such as benzoyl peroxide, and the like. Preferably, thethermal initiator is 2,2′-azobis(isobutyronitrile) (AIBN).

A “spatial limitation of actinic radiation” refers to an act or processin which energy radiation in the form of rays is directed by, forexample, a mask or screen or combinations thereof, to impinge, in aspatially restricted manner, onto an area having a well definedperipheral boundary. For example, a spatial limitation of UV radiationcan be achieved by using a mask or screen that has a transparent or openregion (unmasked region) surrounded by a UV impermeable region (maskedregion), as schematically illustrated in FIGS. 1-9 of U.S. Pat. No.6,627,124 (herein incorporated by reference in its entirety). Theunmasked region has a well defined peripheral boundary with the unmaskedregion. The energy used for the crosslinking is radiation energy,especially UV radiation, gamma radiation, electron radiation or thermalradiation, the radiation energy preferably being in the form of asubstantially parallel beam in order on the one hand to achieve goodrestriction and on the other hand efficient use of the energy.

“Visibility tinting” in reference to a lens means dying (or coloring) ofa lens to enable the user to easily locate a lens in a clear solutionwithin a lens storage, disinfecting or cleaning container. It is wellknown in the art that a dye and/or a pigment can be used in visibilitytinting a lens.

“Dye” means a substance that is soluble in a solvent and that is used toimpart color. Dyes are typically translucent and absorb but do notscatter light. Any suitable biocompatible dye can be used in the presentinvention.

A “Pigment” means a powdered substance that is suspended in a liquid inwhich it is insoluble. A pigment can be a fluorescent pigment,phosphorescent pigment, pearlescent pigment, or conventional pigment.While any suitable pigment may be employed, it is presently preferredthat the pigment be heat resistant, non-toxic and insoluble in aqueoussolutions.

“Surface modification”, as used herein, means that an article has beentreated in a surface treatment process (or a surface modificationprocess) prior to or posterior to the formation of the article, in which(1) a coating is applied to the surface of the article, (2) chemicalspecies are adsorbed onto the surface of the article, (3) the chemicalnature (e.g., electrostatic charge) of chemical groups on the surface ofthe article are altered, or (4) the surface properties of the articleare otherwise modified. Exemplary surface treatment processes include,but are not limited to, plasma processes in which an ionized gas isapplied to the surface of an article (see, for example, U.S. Pat. Nos.4,312,575 and 4,632,844 herein incorporated by reference in itsentirety); a surface treatment by energy other than plasma (e.g., astatic electrical charge, irradiation, or other energy source); chemicaltreatments; the grafting of hydrophilic monomers or macromers onto thesurface of an article; mold-transfer coating process disclosed in U.S.Pat. No. 6,719,929 (herein incorporated by reference in its entirety);the incorporation of wetting agents into a lens formulation for makingcontact lenses (i.e., surface treatment prior to polymerization)proposed in U.S. Pat. Nos. 4,045,547, 4,042,552, 5,198,477, 5,219,965,6,367,929 and 6,822,016, 7,279,507 (herein incorporated by references intheir entireties); reinforced mold-transfer coating disclosed in PCTPatent Application Publication No. WO2007/146137 (herein incorporated byreference in its entirety); and layer-by-layer coating (“LbL coating”)obtained according to methods described in U.S. Pat. Nos. 6,451,871,6,719,929, 6,793,973, 6,811,805, 6,896,926 (herein incorporated byreferences in their entireties).

Exemplary plasma gases and processing conditions are described in U.S.Pat. Nos. 4,312,575 and 4,632,844. The plasma gas is preferably amixture of lower alkanes and nitrogen, oxygen or an inert gas.

“LbL coating”, as used herein, refers to a coating that is notcovalently attached to a contact lens or a mold half and is obtainedthrough a layer-by-layer (“LbL”) deposition of polyionic (or charged)and/or non-charged materials on the lens or mold half. An LbL coatingcan be composed of one or more layers.

As used herein, a “polyionic material” refers to a polymeric materialthat has a plurality of charged groups or ionizable groups, such aspolyelectrolytes, p- and n-type doped conducting polymers. Polyionicmaterials include both polycationic (having positive charges) andpolyanionic (having negative charges) materials.

Formation of an LbL coating on a contact lens or mold half may beaccomplished in a number of ways, for example, as described in U.S. Pat.Nos. 6,451,871, 6,719,929, 6,793,973, 6,811,805, 6,896,926 (hereinincorporated by references in their entirety).

An “antimicrobial agent”, as used herein, refers to a chemical that iscapable of decreasing or eliminating or inhibiting the growth ofmicroorganisms such as that term is known in the art.

“Antimicrobial metals” are metals whose ions have an antimicrobialeffect and which are biocompatible. Preferred antimicrobial metalsinclude Ag, Au, Pt, Pd, Ir, Sn, Cu, Sb, Bi and Zn, with Ag being mostpreferred.

“Antimicrobial metal-containing nanoparticles” refer to particles havinga size of less than 1 micrometer and containing at least oneantimicrobial metal present in one or more of its oxidation states.

“Antimicrobial metal nanoparticles” refer to particles which is madeessentially of an antimicrobial metal and have a size of less than 1micrometer. The antimicrobial metal in the antimicrobial metalnanoparticles can be present in one or more of its oxidation states. Forexample, silver-containing nanoparticles can contain silver in one ormore of its oxidation states, such as Ag⁰, Ag¹⁺, and Ag²⁺.

“Stabilized antimicrobial metal nanoparticles” refer to antimicrobialmetal nanoparticles which are stabilized by a stabilizer during theirpreparation. Stabilized antimicrobial metal nano-particles can be eitherpositively charged or negatively charged or neutral, largely dependingon a material (or so-called stabilizer) which is present in a solutionfor preparing the nano-particles and can stabilize the resultantnano-particles. A stabilizer can be any known suitable material.Exemplary stabilizers include, without limitation, positively chargedpolyionic materials, negatively charged polyionic materials, polymers,surfactants, salicylic acid, alcohols and the like.

The “oxygen transmissibility” of a lens, as used herein, is the rate atwhich oxygen will pass through a specific ophthalmic lens. Oxygentransmissibility, Dk/t, is conventionally expressed in units ofbarrers/mm, where t is the average thickness of the material [in unitsof mm] over the area being measured and “barrer/mm” is defined as:[(cm³ oxygen)/(cm²)(sec)(mm² Hg)]×10⁻⁹

The intrinsic “oxygen permeability”, Dk, of a lens material does notdepend on lens thickness. Intrinsic oxygen permeability is the rate atwhich oxygen will pass through a material. Oxygen permeability isconventionally expressed in units of barrers, where “barrer” is definedas:[(cm³ oxygen)(mm)/(cm²)(sec)(mm² Hg)]×10⁻¹⁰

These are the units commonly used in the art. Thus, in order to beconsistent with the use in the art, the unit “barrer” will have themeanings as defined above. For example, a lens having a Dk of 90 barrers(“oxygen permeability barrers”) and a thickness of 90 microns (0.090 mm)would have a Dk/t of

$100\mspace{14mu}{barrers}\text{/}{{mm}\left( {\frac{90 \times 10^{- 10}}{0.09} = {100 \times 10^{- 9}}} \right)}$(oxygen  transmissibility  barrers/mm).In accordance with the invention, a high oxygen permeability inreference to a material or a contact lens characterized by apparentoxygen permeability of at least 40 barrers or larger measured with asample (film or lens) of 100 microns in thickness according to acoulometric method described in Examples.

The “ion permeability” through a lens correlates with both the IonofluxDiffusion Coefficient and the Ionoton Ion Permeability Coefficient.

The Ionoflux Diffusion Coefficient, D, is determined by applying Fick'slaw as follows:D=−n′/(A×dc/dx)where n′=rate of ion transport [mol/min]

A=area of lens exposed [mm²]

D=Ionoflux Diffusion Coefficient [mm²/min]

dc=concentration difference [mol/L]

dx=thickness of lens [mm]

The Ionoton Ion Permeability Coefficient, P, is then determined inaccordance with the following equation:ln(1−2C(t)/C(0))=−2APt/Vdwhere: C(t)=concentration of sodium ions at time t in the receiving cell

C(0)=initial concentration of sodium ions in donor cell

A=membrane area, i.e., lens area exposed to cells

V=volume of cell compartment (3.0 ml)

d=average lens thickness in the area exposed

P=permeability coefficient

An Ionoflux Diffusion Coefficient, D, of greater than about 1.5×10⁻⁶mm²/min is preferred, while greater than about 2.6×10⁻⁶ mm²/min is morepreferred and greater than about 6.4×10⁻⁶ mm²/min is most preferred.

It is known that on-eye movement of the lens is required to ensure goodtear exchange, and ultimately, to ensure good corneal health. Ionpermeability is one of the predictors of on-eye movement, because thepermeability of ions is believed to be directly proportional to thepermeability of water.

A “reduced E modulus” or “reduced modulus” or “reduced Young's modulus”in reference to a testing silicone hydrogel lens obtained bycrosslinking a first prepolymer with dangling polysiloxane polymerchains is intended to describe that the E modulus (or modulus) of thelens is smaller than a control lens obtained from a second prepolymerwithout dangling polysiloxane polymer chains but having substantiallyidentical amount (by weight) of polysiloxane (based on compositions formaking both the first and second prepolymers).

A “reduction in modulus (ΔE)” of a lens is calculated based on thefollowing formula

${\Delta\; E} = {\frac{E_{control} - E}{E_{control}} \times 100\%}$in which E is the modulus of a testing lens obtained from a firstprepolymer with dangling polysiloxane polymer chains and E_(control) isthe modulus of a control lens obtained from a second prepolymer withoutdangling polysiloxane polymer chains but having substantially identicalamount (by weight) of polysiloxane (based on the compositions for makingboth the first and second prepolymers) as shown in Example 2.

An “increase in ion permeability (Δ(IP))” of a lens is calculated basedon the following formula

${\Delta\;{IP}} = {\frac{{IP} - {IP}_{control}}{{IP}_{control}} \times 100\%}$in which IP is the ion permeability of a testing lens obtained from afirst prepolymer with dangling polysiloxane polymer chains andIP_(control) is the ion permeability of a control lens obtained from asecond prepolymer without dangling polysiloxane polymer chains buthaving substantially identical amount (by weight) of polysiloxane (basedon the compositions for making both the first and second prepolymers) asshown in Example 2.

In general, the invention is directed to a class of actinicallycrosslinkable silicone-containing prepolymers. It is partly based ondiscovery that by incorporating dangling polysiloxane polymer chainsinto an actinically crosslinkable silicone-containing prepolymer, suchprepolymer can be used to produce silicone hydrogel contact lenseshaving a reduced E modulus and substantially equivalent oxygenpermeability. The ion permeability of the resultant lenses can beenhanced by incorporating dangling polysiloxane polymer chains. Suchprepolymers can be used to prepare silicone hydrogel contact lenses, inparticularly according to the Lightstream Technology™ (CIBA Vision).

The present invention, in one aspect, provides an actinicallycrosslinkable prepolymer. The prepolymer of the invention comprises: (1)dangling polysiloxane units derived from one or more monoethylenicallyfunctionalized polysiloxane-containing monomers and/or one or moremonoethylenically-functionalized polysiloxane-containing macromers,wherein the dangling polysiloxane units are free of ethylenicallyunsaturated group; (2) hydrophilic units derived from one or morehydrophilic vinylic monomers; (3) crosslinking units derived from atleast one polysiloxane-containing crosslinker and/or at least onesilicone-free crosslinker; and (4) optionally hydrophobic units derivedfrom at least one hydrophobic vinylic monomer, wherein the prepolymercomprises multiple ethylenically unsaturated groups and is capable ofbeing actinically crosslinked, in the absence of one or more monomers,to form a silicone hydrogel material.

The dangling polysiloxane-containing units of the prepolymer each shouldbe free of any ethylenically unsaturated groups.

In accordance with the invention, a prepolymer of the invention isobtained from an intermediary copolymer with pendant or terminalfunctional group by ethylenically functionalizing the intermediarycopolymer to include multiple ethylenically unsaturated groups,according to any covalently coupling method.

It is well known in the art that a pair of matching reactive groups canform a covalent bond or linkage under known coupling reactionconditions, such as, oxidation-reduction conditions, dehydrationcondensation conditions, addition conditions, substitution (ordisplacement) conditions, Diels-Alder reaction conditions, cationiccrosslinking conditions, and epoxy hardening conditions. For example, anamino group reacts with aldehyde group to form a Schiff base which mayfurther be reduced; an amino group reacts with an acid chloride to forman amide linkage (—CO—N—); an amino group reacts with an isocyanate toform a urea linkage; an hydroxyl reacts with an isocyanate to form aurethane linkage; an hydroxyl reacts with an epoxy to form an etherlinkage (—O—); a hydroxyl reacts with an acid chloride to form an esterlinkage.

Exemplary covalent bonds or linkage, which are formed between pairs ofcrosslinkable groups, include without limitation, ester, ether, acetal,ketal, vinyl ether, carbamate, urea, urethane, amine, amide, enamine,imine, oxime, amidine, iminoester, carbonate, orthoester, phosphonate,phosphinate, sulfonate, sulfinate, sulfide, sulfate, disulfide,sulfinamide, sulfonamide, thioester, aryl, silane, siloxane,heterocycles, thiocarbonate, thiocarbamate, and phosphonamide.

Exemplary reactive groups include hydroxyl group, amine group, amidegroup, anhydride group, sulfhydryl group, —COOR (R and R′ are hydrogenor C₁ to C₈ alkyl groups), halide (chloride, bromide, iodide), acylchloride, isothiocyanate, isocyanate, monochlorotriazine,dichlorotriazine, mono- or di-halogen substituted pyridine, mono- ordi-halogen substituted diazine, phosphoramidite, maleimide, aziridine,sulfonyl halide, hydroxysuccinimide ester, hydroxysulfosuccinimideester, imido ester, hydrazine, axidonitrophenyl group, azide,3-(2-pyridyl dithio)proprionamide, glyoxal, aldehyde, epoxy.

It is understood that coupling agents may be used. For example, acarbodiimide can be used in the coupling of a carboxyl and an amine toform an amide linkage between the molecules being coupled. Examples ofcarbodiimides are 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC),N,N′-dicyclohexylcarbodiimide (DCC),1-cylcohexyl-3-(2-morpholinoethyl)carbodiimide, diisopropylcarbodiimide, or mixtures thereof. N-hydroxysuccinimide (NHS) orN-hydroxysulfosuccinimide may be desirably included in carbodiimide(e.g., EDC)-mediated coupling reaction to improve coupling (conjugation)efficiency. EDC couples NHS to carboxyls, resulting in an NHS-activatedsite on a molecule. The formed NHS-ester can react with amines to formamides.

Preferably, the functional group of the intermediary copolymer isselected from the group consisting of hydroxyl groups (—OH), primaryamino groups (—NH₂), secondary amino groups (—NHR), carboxyl groups(—COOH), epoxy groups, aldehyde groups (—CHO), amide groups (—CONH₂),acid halide groups (—COX, X=Cl, Br, or I), isothiocyanate groups,isocyanate groups, halide groups (—X, X=Cl, Br, or I), acid anhydridegroups, and combinations thereof.

In a preferred embodiment, the intermediary copolymer with pendant orterminal functional groups is obtained by copolymerization of apolymerizable composition comprising (1) at least one monoethylenicallyfunctionalized polysiloxane-containing monomer and/or at least onemonoethylenically unsaturated polysiloxane-containing macromer, (2) atleast one hydrophilic vinylic monomer (i.e., having one ethylenicallyunsaturated group), (3) at least one polysiloxane-containing crosslinkerand/or at least one silicone-free crosslinker, and (4) optionally atleast one hydrophobic vinylic monomer, provided that at least one ofcomponents (2)-(4) further comprises at least one functional groupthrough which an ethylenically unsaturated group can be covalentlylinked to the obtained intermediary copolymer.

In another preferred embodiment, the intermediary copolymer with pendantor terminal functional groups is obtained by copolymerization of acomposition comprising (1) at least one monoethylenically functionalizedpolysiloxane-containing monomer and/or at least one monoethylenicallyunsaturated polysiloxane-containing macromer, (2) at least onehydrophilic vinylic monomer (i.e., having one ethylenically unsaturatedgroup), (3) at least one polysiloxane-containing crosslinker and/or atleast one silicone-free crosslinker, (4) optionally at least onehydrophobic vinylic monomer, and (5) at least one chain transfer agenthaving a functional group through which an ethylenically unsaturatedgroup can be covalently linked to the obtained intermediary copolymer.

Any known suitable monoethylenically functionalizedpolysiloxane-containing monomers or macromers (i.e.,polysiloxane-containing monomers or macromers with one soleethylenically unsaturated group) can be used in the actinicallypolymerizable composition for preparing the intermediary copolymer withpendant or terminal functional groups.

A preferred class of monoethylenically functionalizedpolysiloxane-containing monomers or macromers are those defined byformula (I)

in which X denotes —COO—, —CONR₁₄—, —OCOO—, or —OCONR₁₄—, where each R₁₄is independently H or C₁-C₇ alkyl; R₁₁ denotes a divalent C₁-C₂₅ alkylor C₆-C₃₀ aryl radical, which may interrupted by —O—, —COO—, —CONR₁₄—,—OCOO— or —OCONR₁₄— and may comprise hydroxy group, primary, secondary,or tertiary amine group, carboxy group, or carboxylic acid; R₁₂ is amonovalent C₁-C₂₅ alkyl or C₆-C₃₀ aryl radical, which may interrupted by—O—, —COO—, —CONR₁₄—, —OCOO— or —OCONR₁₄— and may comprise hydroxygroup, primary, secondary, or tertiary amine group, carboxy group, orcarboxylic acid; R₃, R₄, R₅′, R₆, R₇, R₈, R₉ and R₁₀, independently ofone another, are C₁-C₈-alkyl, C₁-C₄ alkyl- or C₁-C₄-alkoxy-substitutedphenyl, fluoro(C₁-C₁₈-alkyl), cyano(C₁-C₁₂-alkyl), hydroxy-C₁-C₆-alkylor amino-C₁-C₆-alkyl; x is the number 0 or 1, m and p independently ofeach other are an integer of from 5 to 700 and (m+p) is from 5 to 700.Preferred examples of such monomers or macromers are monomethacrylatedor monoacrylated polydimethylsiloxanes of various molecular weight(e.g., mono-3-methacryloxypropyl terminated, mono-butyl terminatedpolydimethylsiloxane or mono-(3-methacryloxy-2-hydroxypropyloxy)propylterminated, mono-butyl terminated polydimethylsiloxane). Alternatively,monoethylenically functionalized polysiloxanes can be obtained byethylenically functionalizing of a monofunctionalized polysiloxanes(i.e., with one sole terminal functional group, such as, e.g., —NH₂,—OH, —COOH, epoxy group, etc.) as described above. Suitablemonofunctionalized polysiloxanes are commercially available, e.g., fromAldrich, ABCR GmbH & Co., Fluorochem, or Gelest, Inc, Morrisville, Pa.

Nearly any hydrophilic vinylic monomer can be used in the actinicallypolymerizable composition for preparing the intermediary copolymer withpendant or terminal functional groups. Suitable hydrophilic vinylicmonomers are, without this being an exhaustive list,hydroxyl-substituted hydroxyl-substituted C₁-C₈ alkylacrylates andmethacrylates, acrylamide, methacrylamide, C₁-C₈ alkylacrylamides, C₁-C₈alkylmethacrylamides, ethoxylated acrylates, ethoxylated methacrylates,hydroxyl-substituted C₁-C₈ alkylacrylamides, hydroxyl-substituted C₁-C₈alkylmethacrylamides, hydroxyl-substituted lower alkyl vinyl ethers,sodium vinylsulfonate, sodium styrenesulfonate,2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrole,N-vinyl-2-pyrrolidone, 2-vinyloxazoline,2-vinyl4,4′-dialkyloxazolin-5-one, 2- and 4-vinylpyridine, vinylicallyunsaturated carboxylic acids having a total of 3 to 5 carbon atoms,amino(lower alkyl)—(where the term “amino” also includes quaternaryammonium), mono(lower alkylamino)(lower alkyl) and di(loweralkylamino)(lower alkyl)acrylates and methacrylates, allyl alcohol,N-vinyl alkylamide, N-vinyl-N-alkylamide, and the like.

Among the preferred hydrophilic vinylic monomers areN,N-dimethylacrylamide (DMA), 2-hydroxyethylmethacrylate (HEMA),2-hydroxyethyl acrylate (HEA), hydroxypropyl acrylate, hydroxypropylmethacrylate (HPMA), trimethylammonium 2-hydroxy propylmethacrylatehydrochloride, aminopropyl methacrylate hydrochloride,dimethylaminoethyl methacrylate (DMAEMA), glycerol methacrylate (GMA),N-vinyl-2-pyrrolidone (NVP), dimethylaminoethylmethacrylamide,acrylamide, methacrylamide, allyl alcohol, vinylpyridine,N-(1,1dimethyl-3-oxobutyl)acrylamide, acrylic acid, a C₁-C₄-alkoxypolyethylene glycol (meth)acrylate having a weight average molecularweight of from 200 to 1500, methacrylic acid, N-vinyl formamide, N-vinylacetamide, N-vinyl isopropylamide, N-vinyl-N-methyl acetamide, allylalcohol, and N-vinyl caprolactam.

In accordance with the invention, polysiloxane-containing crosslinkersrefers to polysiloxane-containing compounds, macromers or prepolymer,which comprises two or more ethylenically unsaturated groups. Examplesof polysiloxane-containing crosslinkers include without limitationdimethacrylated or diacrylated polydimethylsiloxanes of variousmolecular weight; vinyl terminated polydimethylsiloxanes of variousmolecular weight; methacrylamide-terminated polydimethylsiloxanes;acrylamide-terminated polydimethylsiloxanes; acrylate-terminatedpolydimethylsiloxanes; methacrylate-terminated polydimethylsiloxanes;bis-3-methacryloxy-2-hydroxypropyloxypropyl polydimethylsiloxane;N,N,N′,N′-tetrakis(3-methacryloxy-2-hydroxypropyl)-alpha,omega-bis-3-aminopropyl-polydimethylsiloxane;polysiloxane-containing macromer selected from the group consisting ofMacromer A, Macromer B, Macromer C, and Macromer D described in U.S.Pat. No. 5,760,100 (herein incorporated by reference in its entirety);the reaction products of glycidyl methacrylate with amino-functionalpolydimethylsiloxanes; polysiloxane-containing prepolymers disclosed inU.S. Pat. No. 6,762,264 (here incorporated by reference in itsentirety); prepolymers disclosed in PCT patent application publicationNo. WO00/59970 (herein incorporated by reference in its entirety);prepolymers disclosed in U.S. Pat. No. 7,091,283 (herein incorporated byreference in its entirety); polysiloxane crosslinkers andpolysiloxane/perfluoroalkyl ether block copolymer crosslinkers disclosedin U.S. Pat. No. 7,091,283 (herein incorporated by reference in itsentirety); di and triblock macromers consisting of polydimethylsiloxaneand polyalkyleneoxides (e.g., methacrylate end cappedpolyethyleneoxide-block-polydimethylsiloxane-block-polyethyleneoxide);and mixtures thereof. It is understood that perfluoroalkyl ethercrosslinkers, such as those disclosed in U.S. Pat. No. 7,091,283 (hereinincorporated by reference in its entirety), can also be used ascrosslinkers in the invention.

Alternatively, di- or multi-ethylenically functionalized polysiloxanescan be obtained by ethylenically functionalizing of a di- ormulti-functionalized polysiloxanes (i.e., with two or more terminalfunctional groups, such as, e.g., —NH₂, —OH, —COOH, epoxy groups, etc.)as described above. Suitable di- or multi-functionalized polysiloxanesare commercially available, e.g., from Aldrich, ABCR GmbH & Co.,Fluorochem, or Gelest, Inc, Morrisville, Pa.

In accordance with the invention, silicone-free crosslinkers are vinyliccompounds, macromers, or prepolymers, having two or more ethylenicallyunsaturated groups.

Examples of silicone-free crosslinkers include without limitationtetraethyleneglycol dimethacrylate (TEGDMA), triethyleneglycoldimethacrylate (TrEGDMA), ethyleneglycol dimethacylate (EGDMA),ethylenediamine dimethyacrylamide, glycerol dimethacrylate andcombinations thereof.

Examples of hydrophilic prepolymers with multiple acryloyl ormethacryloyl groups (as silicone-free crosslinkers) include, but are notlimited to, a water-soluble crosslinkable poly(vinyl alcohol) prepolymerdescribed in U.S. Pat. Nos. 5,583,163 and 6,303,687; a water-solublevinyl group-terminated polyurethane prepolymer described in U.S. PatentApplication Publication No. 2004/0082680; derivatives of a polyvinylalcohol, polyethyleneimine or polyvinylamine, which are disclosed inU.S. Pat. No. 5,849,841; a water-soluble crosslinkable polyureaprepolymer described in U.S. Pat. No. 6,479,587 and in U.S. PublishedApplication No. 2005/0113549; crosslinkable polyacrylamide;crosslinkable statistical copolymers of vinyl lactam, MMA and acomonomer, which are disclosed in EP 655,470 and U.S. Pat. No.5,712,356; crosslinkable copolymers of vinyl lactam, vinyl acetate andvinyl alcohol, which are disclosed in EP 712,867 and U.S. Pat. No.5,665,840; polyether-polyester copolymers with crosslinkable side chainswhich are disclosed in EP 932,635 and U.S. Pat. No. 6,492,478; branchedpolyalkylene glycol-urethane prepolymers disclosed in EP 958,315 andU.S. Pat. No. 6,165,408; polyalkylene glycol-tetra(meth)acrylateprepolymers disclosed in EP 961,941 and U.S. Pat. No. 6,221,303; andcrosslinkable polyallylamine gluconolactone prepolymers disclosed inInternational Application No. WO 2000/31150 and U.S. Pat. No. 6,472,489.

Nearly any hydrophobic vinylic monomer can be used in the actinicallypolymerizable composition for preparing the intermediary copolymer withpendant or terminal functional groups. Suitable hydrophobic vinylicmonomers include, without limitation, silicone-containing vinylicmonomers, C₁-C₁₈-alkylacrylates and -methacrylates, C₃-C₁₈alkylacrylamides and -methacrylamides, acrylonitrile, methacrylonitrile,vinyl-C₁-C₁₈-alkanoates, C₂-C₁₈-alkenes, C₂-C₁₈-halo-alkenes, styrene,C₁-C₆-alkylstyrene, vinylalkylethers in which the alkyl moiety has 1 to6 carbon atoms, C₂-C₁₀-perfluoralkyl-acrylates and -methacrylates orcorrespondingly partially fluorinated acrylates and methacrylates,C₃-C₁₂-perfluoralkyl-ethyl-thiocarbonylaminoethyl-acrylates and-methacrylates, acryloxy and methacryloxy-alkylsiloxanes,N-vinylcarbazole, C₁-C₁₂-alkylesters of maleic acid, fumaric acid,itaconic acid, mesaconic acid and the like. Preference is given e.g. toC₁-C₄-alkylesters of vinylically unsaturated carboxylic acids with 3 to5 carbon atoms or vinylesters of carboxylic acids with up to 5 carbonatoms.

Examples of preferred hydrophobic vinylic monomers includemethylacrylate, ethyl-acrylate, propylacrylate, isopropylacrylate,cyclohexylacrylate, 2-ethylhexylacrylate, methylmethacrylate,ethylmethacrylate, propyl methacrylate, vinyl acetate, vinyl propionate,vinyl butyrate, vinyl valerate, styrene, chloroprene, vinyl chloride,vinylidene chloride, acrylonitrile, 1-butene, butadiene,methacrylonitrile, vinyl toluene, vinyl ethyl ether,perfluorohexylethyl-thio-carbonyl-aminoethyl-methacrylate, isobornylmethacrylate, trifluoroethyl methacrylate, hexafluoro-isopropylmethacrylate, and hexafluorobutyl methacrylate.

The chain transfer agent may comprise one or more thiol groups, forexample two or most preferably one thiol group. Suitable chain transferagents include without limitation 2-mercaptoethanol, 2-aminoethanethiol,2-mercaptopropinic acid, thioglycolic acid, thiolactic acid, or otherhydroxymercaptanes, aminomercaptans, carboxyl-containing mercaptanes,and mixtures thereof. Where a chain transfer agent comprises afunctional group in addition to one or more thiol groups, it can beincorporated into the resultant intermediary copolymer and providefunctionality for subsequent addition of an ethylenically unsaturatedgroup to the intermediary copolymer. A chain transfer agent can also beused to control the molecular weight of the resultant copolymer.

Any know suitable vinylic monomer containing at least one functionalgroup can be used in the actinically polymerizable composition forpreparing the intermediary copolymer with pendant or terminal functionalgroups. The functional groups of units derived from such vinylic monomercan be used in ethylenically functionalizing the intermediarycopolymers. Preferred examples of such vinylic monomers includesmethacrylic acid (MAA), acrylic acid, glycidylmethacrylate,glycidylacrylate, HEMA, HEA, aminopropyl methacrylate hydrochloride,methacrylic anhydride, N-hydroxymethylacrylamide (NHMA),2-bromoethylmethacrylate, and vinylbenzylchloride.

It should be understood that a vinylic monomer can be used both as ahydrophilic vinylic monomer and as a functionalizing vinylic monomer inthe actinically polymerizable composition for preparing the intermediarycopolymer with pendant or terminal functional groups. Preferably, thehydrophilic vinylic monomer is devoid of functional groups (e.g., DMA,NVP).

In another preferred embodiment, a polymerizable composition for makingan intermediary copolymer of the invention further comprises at leastone silicone-containing vinylic monomer.

Examples of preferred silicone-containing vinylic monomers (i.e., withone sole ethylenically unsaturated group) include, without limitation,3-methacryloxy propylpentamethyldisiloxane,bis(methacryloxypropyl)tetramethyl-disiloxane,N-[tris(trimethylsiloxy)silylpropyl]acrylamide,N-[tris(trimethylsiloxy)silylpropyl]methacrylamide, andtristrimethylsilyloxysilylpropyl methacrylate (TRIS),N-[tris(trimethylsiloxy)silylpropyl]methacrylamide (“TSMAA”),N-[tris(trimethylsiloxy)-silylpropyl]acrylamide (“TSAA”),(3-methacryloxy-2-hydroxypropyloxy)propylbis(trimethylsiloxy)methylsilane),(3-methacryloxy-2-hydroxypropyloxy)propyltris(trimethylsiloxy)silane,3-methacryloxy-2-(2-hydroxyethoxy)propyloxy)propylbis(trimethylsiloxy)methylsilane,N-2-methacryloxyethyl-O-(methyl-bis-trimethylsiloxy-3-propyl)silylcarbamate, silicone-containing vinyl carbonate or vinyl carbamatemonomers (e.g.,1,3-bis[4-vinyloxycarbonyloxy)but-1-yl]tetramethyl-disiloxane;3-(trimethylsilyl), propyl vinyl carbonate,3-(vinyloxycarbonylthio)propyl-[tris(trimethylsiloxy)silane],3-[tris(trimethylsiloxy)silyl]propylvinyl carbamate,3-[tris(trimethylsiloxy)silyl]propyl allyl carbamate,3-[tris(trimethylsiloxy)silyl]propyl vinyl carbonate,t-butyldimethylsiloxyethyl vinyl carbonate; trimethylsilylethyl vinylcarbonate, and trimethylsilylmethyl vinyl carbonate).

The polymerizable composition for preparing an intermediary copolymercan be a melt, a solventless liquid in which all necessary componentsare blended together preferably in the presence of one or more blendingvinylic monomers, or a solution in which all necessary component isdissolved in a solvent, such as water, an organic solvent, or mixturethereof, as known to a person skilled in the art.

Example of organic solvents includes without limitation tetrahydrofuran,tripropylene glycol methyl ether, dipropylene glycol methyl ether,ethylene glycol n-butyl ether, diethylene glycol n-butyl ether,diethylene glycol methyl ether, ethylene glycol phenyl ether, propyleneglycol methyl ether, propylene glycol methyl ether acetate, dipropyleneglycol methyl ether acetate, propylene glycol n-propyl ether,dipropylene glycol n-propyl ether, tripropylene glycol n-butyl ether,propylene glycol n-butyl ether, dipropylene glycol n-butyl ether,tripropylene glycol n-butyl ether, propylene glycol phenyl etherdipropylene glycol dimethyl ether, polyethylene glycols, polypropyleneglycols, ethyl acetate, butyl acetate, amyl acetate, methyl lactate,ethyl lactate, i-propyl lactate, methylene chloride, 2-butanol,2-propanol, menthol, cyclohexanol, cyclopentanol and exonorborneol,2-pentanol, 3-pentanol, 2-hexanol, 3-hexanol, 3-methyl-2-butanol,2-heptanol, 2-octanol, 2-nonanol, 2-decanol, 3-octanol, norborneol,tert-butanol, tert-amyl alcohol, 2-methyl-2-pentanol,2,3-dimethyl-2-butanol, 3-methyl-3-pentanol, 1-methylcyclohexanol,2-methyl-2-hexanol, 3,7-dimethyl-3-octanol,1-chloro-2-methyl-2-propanol, 2-methyl-2-heptanol, 2-methyl-2-octanol,2-2-methyl-2-nonanol, 2-methyl-2-decanol, 3-methyl-3-hexanol,3-methyl-3-heptanol, 4-methyl-4-heptanol, 3-methyl-3-octanol,4-methyl-4-octanol, 3-methyl-3-nonanol, 4-methyl-4-nonanol,3-methyl-3-octanol, 3-ethyl-3-hexanol, 3-methyl-3-heptanol,4-ethyl-4-heptanol, 4-propyl-4-heptanol, 4-isopropyl-4-heptanol,2,4-dimethyl-2-pentanol, 1-methylcyclopentanol, 1-ethylcyclopentanol,1-ethylcyclopentanol, 3-hydroxy-3-methyl-1-butene,4-hydroxy-4-methyl-1-cyclopentanol, 2-phenyl-2-propanol,2-methoxy-2-methyl-2-propanol 2,3,4-trimethyl-3-pentanol,3,7-dimethyl-3-octanol, 2-phenyl-2-butanol, 2-methyl-1-phenyl-2-propanoland 3-ethyl-3-pentanol, 1-ethoxy-2-propanol, 1-methyl-2-propanol, t-amylalcohol, isopropanol, 1-methyl-2-pyrrolidone, N,N-dimethylpropionamide,dimethyl formamide, dimethyl acetamide, dimethyl propionamide,N-methylpyrrolidinone, and mixtures thereof.

The one or more blending vinylic monomers are in an amount sufficient todissolve both hydrophilic and hydrophobic components of the actinicallypolymerizable composition. A “blending vinylic monomer” refers to avinylic monomer which can function both as a solvent to dissolve bothhydrophilic and hydrophobic components of an actinically polymerizablecomposition and as one of polymerizable components to be polymerized toform a silicone hydrogel material. Preferably, the blending vinylicmonomer is present in the actinically polymerizable composition in anamount of from about 5% to about 30% by weight.

Any suitable vinylic monomers, capable of dissolving both hydrophilicand hydrophobic components of a polymerizable composition of theinvention to form a solution, can be used in the invention. Preferredexamples of blending vinylic monomers include, without limitation,aromatic vinylic monomers, cycloalkyl-containing vinylic monomers. Thosepreferred blending monomers can increase the predominant glasstransition temperature of a silicone hydrogel material prepared bycuring a polymerizable composition containing those preferred blendingmonomer.

Examples of preferred aromatic vinylic monomers include styrene,2,4,6-trimethylstyrene (TMS), t-butyl styrene (TBS),2,3,4,5,6-pentafluorostyrene, benzyl methacrylate, divinylbenzene, and2-vinylnaphthalene. Of these monomers, a styrene-containing monomer ispreferred. A styrene-containing monomer is defined herein to be amonomer that contains a vinyl group bonded directly to a phenyl group inwhich the phenyl group can be substituted by other than a fused ring,e.g., as above with one to three C₁-C₆ alkyl groups. Styrene itself[H₂C═CH—C₆H₅] is a particularly preferred styrene-containing monomer.

A cycloalkyl-containing vinylic monomer is defined herein to be avinylic monomer containing a cycloalkyl which can be substituted by upto three C₁-C₆ alkyl groups. Preferred cycloalkyl-containing vinylicmonomers include, without limitation, acrylates and methacrylates eachcomprising a cyclopentyl or cyclohexyl or cycloheptyl, which can besubstituted by up to 3 C₁-C₆ alkyl groups. Examples of preferredcycloalkyl-containing vinylic monomers include isobornylmethacrylate,isobornylacrylate, cyclohexylmethacrylate, cyclohexylacrylate, and thelike.

The stoichiometry of the hydrophilic monomer, crosslinker and chaintransfer agent in the polymerizable composition for preparing anintermediary copolymer may be chosen within wide limits and is stronglydependant on the intended use. For example, a molar ratio of from 0.5 to5 equivalents chain transfer agent: 1-3 equivalents monoethylenicallyfunctionalized polysiloxane-containing monomer and macromer (in total):1equivalent crosslinker (including polysiloxane-containing crosslinkerand silicone-free crosslinker): 5 to 60 equivalents hydrophilicmonomer(s) has proven as practicable for biomedical purposes. Apreferred range is from 1 to 3 molar equivalents chain transfer agent:1-3 equivalents monoethylenically functionalized polysiloxane-containingmonomer and macromer (in total): 1 equivalent crosslinker (includingpolysiloxane-containing crosslinker and silicone-free crosslinker): 10to 50 molar equivalents hydrophilic monomer(s).

The weight average molecular weight of the resulting copolymers isstrongly dependent, for example, on the amount of chain transfer agentused, preferably from 3000 to 1000000, preferably from 5000 to 500000,more preferably from 7000 to 250000 daltons.

The copolymerization of a polymerizable composition for preparing anintermediary copolymer may be induced photochemically or preferablythermally. Suitable thermal polymerization initiators are known to theskilled artisan and comprise, for example peroxides, hydroperoxides,azo-bis(alkyl- or cycloalkylnitriles), persulfates, percarbonates ormixtures thereof. Examples are benzoylperoxide, tert.-butyl peroxide,di-tert.-butyl-diperoxyphthalate, tert.-butyl hydroperoxide,azo-bis(isobutyronitrile) (AIBN), 1,1-azodiisobutyramidine, 1,1′-azo-bis(1-cyclohexanecarbonitrile), 2,2′-azo-bis(2,4-dimethylvaleronitrile) andthe like. The polymerization is carried out conveniently in anabove-mentioned solvent at elevated temperature, for example at atemperature of from 25 to 100° C. and preferably 40 to 80° C. Thereaction time may vary within wide limits, but is conveniently, forexample, from 1 to 24 hours or preferably from 2 to 12 hours. It isadvantageous to previously degas the components and solvents used in thepolymerization reaction and to carry out said copolymerization reactionunder an inert atmosphere, for example under a nitrogen or argonatmosphere. Copolymerization can yield optically clear well-definedcopolymers which may be worked up in conventional manner using forexample extraction, precipitation, ultrafiltration and the liketechniques.

In a preferred embodiment, the dangling polysiloxane units is present inthe prepolymer in an amount sufficient to provide the lens made from theprepolymer with a reduction in modulus of at least about 10% or more,preferably at least about 20% or more, even more preferably at leastabout 30% or more, most preferably at least about 40% or more.

In another preferred embodiment, the dangling polysiloxane units ispresent in the prepolymer in an amount sufficient to provide the lensmade from the prepolymer with an increase in ion permeability of atleast about 20% or more, preferably at least about 40% or more, evenmore preferably at least about 60% or more.

The amount of the dangling polysiloxane units in the prepolymer can bechanged by adjusting the amount of the one or more monoethylenicallyfunctionalized polysiloxane-containing monomers and/or one or moremonoethylenically-functionalized polysiloxane-containing macromers inthe polymerizable composition for preparing the intermediary copolymerwith pendant or terminal functional groups while maintaining the totalweight percentage of all polysiloxane-containing polymerizablecomponents.

Preferably, a prepolymer of the invention comprises: (1) from about 2%to about 70% by weight, preferably from about 5% to about 40%, ofdangling polysiloxane units derived from one or more monoethylenicallyfunctionalized polysiloxane-containing monomers and/or macromers; (2)from about 10% to about 70%, preferably from about 20% to 60% by weight,by weight of hydrophilic units derived from one or more hydrophilicmonomers; (3) from 0 to about 70%, preferably from about 1% to about60%, more preferably from about 5% to about 50% by weight ofcrosslinking polysiloxane units derived from a polysiloxane-containingcrosslinker; (4) from 0 to about 5%, more preferably from 0 to about 2%by weight of silicone-free crosslinker; and (5) from about 0 to about35%, preferably from about 1% to about 30% by weight ofsilicone-containing units derived from one or more silicone-containingvinylic monomers.

In accordance with the invention, ethylenical functionalization of theintermediary copolymer can be carried out by covalently attachingethylenically unsaturated groups to the functional groups (e.g., amine,hydroxyl, carboxyl, isocyanate, epoxy groups) of the intermediarycopolymer. Any vinylic monomer having a hydroxy, amino, carboxyl, epoxy,acid-chloride, isocyanate group, which is co-reactive with isocyanate,amine, hydroxyl, carboxy, or epoxy groups of an intermediary copolymerin the absence or presence of a coupling agent (such as, e.g., EDC,diisocyanate, or diacid chloride), can be used in ethylenicallyfunctionalizing the intermediary copolymer. Examples of such vinylicmonomers include, without limitation, for reacting with terminal hydroxygroups, 2-isocyanatoethyl methacrylate, methacrylic anhydride,3-isopropenyl-alpha, alpha-dimethylbenzyl isocyanate, acryloyl chloride,or methacryloyl chloride, glycidyl methacrylate; for reacting withterminal amine groups, 2-isocyanatoethyl methacrylate,3-isopropenyl-alpha, alpha-dimethylbenzyl isocyanate, methacrylicanhydride, acrylic acid, methacrylic acid, acryloyl chloride, ormethacryloyl chloride; for reacting with terminal carboxy groups in thepresence of EDC, vinylamine, 2-aminoethyl methacrylate or 3-aminopropylmethacrylamide. The above list is not exhaustive but illustrative. Aperson skilled in the art will know how to select a vinylic monomer witha functional group to functionalize ethylenically intermediarycopolymers.

A prepolymer of the invention is capable of forming, preferably in theabsence of any hydrophilic vinylic monomer, a silicone hydrogel orcontact lens, which has a high oxygen permeability (characterized by anapparent oxygen permeability of at least 40 barrers, preferably at leastabout 60 barrers, even more preferably at least 80 barrers) and anelastic modulus of preferably about 1.5 MPa or less, more preferablyabout 1.2 or less, even more preferably from about 0.4 MPa to about 1.0MPa. By having a higher percentage of dangling polysiloxane units thancrosslinked polysiloxane units, a prepolymer of the invention can beused to prepare silicone hydrogel contact lenses having a relatively lowelastic modulus while having a relatively high oxygen permeability.

The silicone hydrogel material or contact lens preferably has a high ionpermeability (characterized by an Ionoflux Diffusion Coefficient, D, ofgreater than about 1.5×10⁻⁶ mm²/min, preferably greater than about2.6×10⁻⁶ mm²/min, more preferably greater than about 6.4×10⁻⁶ mm²/min).The silicone hydrogel material or contact lens preferably has a watercontent of preferably from about 18% to about 55%, more preferably fromabout 20% to about 38% by weight when fully hydrated. The water contentof a silicone hydrogel contact lens can be measured according to BulkTechnique as disclosed in U.S. Pat. No. 5,849,811.

Preferably, the prepolymers used in the invention are previouslypurified in a manner known per se, for example by precipitation withorganic solvents, such as acetone, filtration and washing, extraction ina suitable solvent, dialysis or ultrafiltration, ultrafiltration beingespecially preferred. By means of that purification process theprepolymers can be obtained in a pure form, for example in the form ofconcentrated solutions that are free, or at least substantially free,from reaction products, such as salts, and from starting materials, suchas, for example, non-polymeric constituents. The preferred purificationprocess for the prepolymers used in the process according to theinvention, ultrafiltration, can be carried out in a manner known per se.It is possible for the ultrafiltration to be carried out repeatedly, forexample from two to ten times. Alternatively, the ultrafiltration can becarried out continuously until the selected degree of purity isattained. The selected degree of purity can, in principle, be as high asdesired. A suitable measure for the degree of purity is, for example,the concentration of dissolved salts obtained as by-products, which canbe determined simply in a known manner. Thus, after polymerization, thedevice will not require subsequent purification such as, for example,costly and complicated extraction of unpolymerized matrix-formingmaterial. Furthermore, crosslinking of the prepolymer can take placeabsent a solvent or in aqueous solution so that a subsequent solventexchange or the hydration step is not necessary.

In another aspect, the invention provides a soft contact lens. The softcontact lens of the invention comprises: a silicone hydrogel materialthat is obtained by curing a lens-forming material in a mold, whereinthe lens-forming material comprises an actinically crosslinkableprepolymer and is substantially free of vinylic monomers andcrosslinking agent with molecular weight of less than 1500 dalton,wherein the prepolymer comprises (1) dangling polysiloxane units derivedfrom one or more monoethylenically functionalizedpolysiloxane-containing monomers and/or one or moremonoethylenically-functionalized polysiloxane-containing macromers,wherein the dangling polysiloxane units is free of ethylenicallyunsaturated groups; (2) hydrophilic units derived from one or morehydrophilic vinylic monomers; (3) crosslinking units derived from atleast one polysiloxane-containing crosslinker and/or at least onesilicone-free crosslinker; (4) multiple ethylenically unsaturatedgroups; and (5) optionally hydrophobic units derived from at least onehydrophobic vinylic monomer.

In accordance with the invention, a lens-forming material is acomposition, which can be a solution or a melt at a temperature fromabout 20° C. to about 85° C. Preferably, a lens-forming material is asolution of at least one prepolymer of the invention and other desirablecomponents in water, or an organic solvent, or a mixture of water andone or more organic solvents.

A solution of at least one prepolymer can be prepared by dissolving theprepolymer and other components in any suitable solvent known to aperson skilled in the art. Examples of suitable solvents are describedabove.

All of the various embodiments of the prepolymer of the inventiondescribed above can be used in this aspect of the invention.

The lens-forming material can optionally but preferably does notcomprise one or more vinylic monomer and/or one or more crosslinkingagents (i.e., compounds with two or more ethylenically unsaturatedgroups and with molecular weight less than 700 Daltons). However, theamount of those components should be low such that the final ophthalmicdevice does not contain unacceptable levels of unpolymerized monomersand/or crosslinking agents. The presence of unacceptable levels ofunpolymerized monomers and/or crosslinking agents will requireextraction to remove them, which requires additional steps that arecostly and inefficient. But preferably, the lens-forming material issubstantially free of vinylic monomer and crosslinking agent (i.e.,preferably about 2% or less, more preferably about 1% or less, even morepreferably about 0.5% or less by weight of combination of vinylicmonomer and crosslinking agent).

It must be understood that a lens-forming material can also comprisevarious components, such as, for example, polymerization initiators(e.g., photoinitiator or thermal initiator), a visibility tinting agent(e.g., dyes, pigments, or mixtures thereof), UV-blocking (absorbing)agent, photosensitizers, inhibitors, antimicrobial agents (e.g.,preferably silver nanoparticles or stabilized silver nanoparticles),bioactive agent, leachable lubricants, fillers, and the like, as knownto a person skilled in the art.

Initiators, for example, selected from materials well known for such usein the polymerization art, may be included in the lens-forming materialin order to promote, and/or increase the rate of, the polymerizationreaction. An initiator is a chemical agent capable of initiatingpolymerization reactions. The initiator can be a photoinitiator or athermal initiator.

A photoinitiator can initiate free radical polymerization and/orcrosslinking by the use of light. Suitable photoinitiators are benzoinmethyl ether, diethoxyacetophenone, a benzoylphosphine oxide,1-hydroxycyclohexyl phenyl ketone and Darocur and Irgacur types,preferably Darocur 1173® and Darocur 2959®. Examples of benzoylphosphineinitiators include 2,4,6-trimethylbenzoyldiphenylophosphine oxide;bis-(2,6-dichlorobenzoyl)-4-N-propylphenylphosphine oxide; andbis-(2,6-dichlorobenzoyl)-4-N-butylphenylphosphine oxide. Reactivephotoinitiators which can be incorporated, for example, into a macromeror can be used as a special monomer are also suitable. Examples ofreactive photoinitiators are those disclosed in EP 632 329, hereinincorporated by reference in its entirety. The polymerization can thenbe triggered off by actinic radiation, for example light, in particularUV light of a suitable wavelength. The spectral requirements can becontrolled accordingly, if appropriate, by addition of suitablephotosensitizers

Examples of suitable thermal initiators include, but are not limited to,2,2′-azobis(2,4-dimethylpentanenitrile),2,2′-azobis(2-methylpropanenitrile), 2,2′-azobis(2-methylbutanenitrile),peroxides such as benzoyl peroxide, and the like. Preferably, thethermal initiator is azobisisobutyronite (AIBN).

Examples of preferred pigments include any colorant permitted in medicaldevices and approved by the FDA, such as D&C Blue No. 6, D&C Green No.6, D&C Violet No. 2, carbazole violet, certain copper complexes, certainchromium oxides, various iron oxides, phthalocyanine green,phthalocyanine blue, titanium dioxides, etc. See Marmiom DM Handbook ofU.S. Colorants for a list of colorants that may be used with the presentinvention. A more preferred embodiment of a pigment include (C.I. is thecolor index no.), without limitation, for a blue color, phthalocyanineblue (pigment blue 15:3, C.I. 74160), cobalt blue (pigment blue 36, C.I.77343), Toner cyan BG (Clariant), Permajet blue B2G (Clariant); for agreen color, phthalocyanine green (Pigment green 7, C.I. 74260) andchromium sesquioxide; for yellow, red, brown and black colors, variousiron oxides; PR122, PY154, for violet, carbazole violet; for black,Monolith black C-K (CIBA Specialty Chemicals).

The bioactive agent incorporated in the polymeric matrix is any compoundthat can prevent a malady in the eye or reduce the symptoms of an eyemalady. The bioactive agent can be a drug, an amino acid (e.g., taurine,glycine, etc.), a polypeptide, a protein, a nucleic acid, or anycombination thereof. Examples of drugs useful herein include, but arenot limited to, rebamipide, ketotifen, olaptidine, cromoglycolate,cyclosporine, nedocromil, levocabastine, lodoxamide, ketotifen, or thepharmaceutically acceptable salt or ester thereof. Other examples ofbioactive agents include 2-pyrrolidone-5-carboxylic acid (PCA), alphahydroxyl acids (e.g., glycolic, lactic, malic, tartaric, mandelic andcitric acids and salts thereof, etc.), linoleic and gamma linoleicacids, and vitamins (e.g., B5, A, B6, etc.).

Examples of leachable lubricants include without limitation mucin-likematerials and non-crosslinkable hydrophilic polymers (i.e., withoutethylenically unsaturated groups). Exemplary mucin-like materialsinclude without limitation polyglycolic acid, polylactides, collagen,hyaluronic acid, and gelatin.

Any hydrophilic polymers or copolymers without any ethylenicallyunsaturated groups can be used as leachable lubricants. Preferredexamples of non-crossllinkable hydrophilic polymers include, but are notlimited to, polyvinyl alcohols (PVAs), polyamides, polyimides,polylactone, a homopolymer of a vinyl lactam, a copolymer of at leastone vinyl lactam in the presence or in the absence of one or morevinylic comonomers, a homopolymer of acrylamide or methacrylamide, acopolymer of acrylamide or methacrylamide with one or more hydrophilicvinylic monomers, polyethylene oxide (i.e., polyethylene glycol (PEG)),a polyoxyethylene derivative, poly-N—N-dimethylacrylamide, polyacrylicacid, poly 2 ethyl oxazoline, heparin polysaccharides, polysaccharides,and mixtures thereof.

The molecular weight of the non-crosslinkable hydrophilic polymer ispreferably from about 20,000 to about 1,500,000 daltons, more preferablyfrom about 50,000 to 1,200,000 daltons, even more preferably from100,000 to 1,000,000 daltons.

In accordance with the invention, the lens-forming material can beintroduced (dispensed) into a cavity formed by a mold according to anyknown methods.

Lens molds for making contact lenses are well known to a person skilledin the art and, for example, are employed in cast molding or spincasting. For example, a mold (for cast molding) generally comprises atleast two mold sections (or portions) or mold halves, i.e. first andsecond mold halves. The first mold half defines a first molding (oroptical) surface and the second mold half defines a second molding (oroptical) surface. The first and second mold halves are configured toreceive each other such that a lens forming cavity is formed between thefirst molding surface and the second molding surface. The moldingsurface of a mold half is the cavity-forming surface of the mold and indirect contact with lens-forming material.

Methods of manufacturing mold sections for cast-molding a contact lensare generally well known to those of ordinary skill in the art. Theprocess of the present invention is not limited to any particular methodof forming a mold. In fact, any method of forming a mold can be used inthe present invention. The first and second mold halves can be formedthrough various techniques, such as injection molding or lathing.Examples of suitable processes for forming the mold halves are disclosedin U.S. Pat. No. 4,444,711 to Schad; U.S. Pat. No. 4,460,534 to Boehm etal.; U.S. Pat. No. 5,843,346 to Morrill; and U.S. Pat. No. 5,894,002 toBoneberger et al., which are also incorporated herein by reference.

Virtually all materials known in the art for making molds can be used tomake molds for preparing ocular lenses. For example, polymericmaterials, such as polyethylene, polypropylene, polystyrene, PMMA,cyclic olefin copolymers (e.g., Topas® COC from Ticona GmbH ofFrankfurt, Germany and Summit, N.J.; Zeonex® and Zeonor® from ZeonChemicals LP, Louisville, Ky.), or the like can be used. Other materialsthat allow UV light transmission could be used, such as quartz, glass,CaF₂, and sapphire.

In a preferred embodiment, when the polymerizable components in thelens-forming material is composed essentially of prepolymers, reusablemolds can be used. Examples of reusable molds made of quartz or glassare those disclosed in U.S. Pat. No. 6,627,124, which is incorporated byreference in their entireties. In this aspect, the lens-forming materialis poured into a mold consisting of two mold halves, the two mold halvesnot touching each other but having a thin gap of annular design arrangedbetween them. The gap is connected to the mold cavity, so that excesslens-forming material can flow into the gap. Instead of polypropylenemolds that can be used only once, it is possible for reusable quartz,glass, sapphire molds to be used, since, following the production of alens, these molds can be cleaned rapidly and effectively to removeunreacted materials and other residues, using water or a suitablesolvent, and can be dried with air. Reusable molds can also be made of acyclic olefin copolymer, such as for example, Topas® COC grade 8007-S10(clear amorphous copolymer of ethylene and norbornene) from Ticona GmbHof Frankfurt, Germany and Summit, N.J., Zeonex® and Zeonor® from ZeonChemicals LP, Louisville, Ky. Because of the reusability of the moldhalves, a relatively high outlay can be expended at the time of theirproduction in order to obtain molds of extremely high precision andreproducibility. Since the mold halves do not touch each other in theregion of the lens to be produced, i.e. the cavity or actual mold faces,damage as a result of contact is ruled out. This ensures a high servicelife of the molds, which, in particular, also ensures highreproducibility of the contact lenses to be produced and high fidelityto the lens design.

After the lens-forming material is dispensed into the mold, it ispolymerized to produce a contact lens. Crosslinking and/or polymerizingmay be initiated in the mold e.g. by means of actinic radiation, such asUV irradiation, ionizing radiation (e.g., gamma or X-ray irradiation).Where prepolymers of the invention are the polymerizable components inthe lens-forming material, the mold containing the lens-forming materialcan be exposed to a spatial limitation of actinic radiation to crosslinkthe prepolymers.

The crosslinking according to the invention may be effected in a veryshort time, e.g. in 60 minutes, advantageously in ≦20 minutes,preferably in ≦10 minutes, most preferably in ≦5 minutes, particularlypreferably in 1 to 60 seconds and most particularly in 1 to 30 seconds.

The contact lenses according to the invention can be produced from oneor more radiation-curable prepolymers of the invention in a very simpleand efficient way compared with the prior art. This is based on manyfactors. On the one hand, the starting materials may be acquired orproduced inexpensively. Secondly, there is the advantage that theprepolymers are surprisingly stable, so that they may undergo a highdegree of purification. There is no practical need for subsequentpurification, such as in particular complicated extraction ofunpolymerized constituents after curing lenses. Furthermore, the newpolymerization method can be used to produce contact lenses withdesirable mechanical and physical properties. Finally,photo-polymerization is effected within a short period, so that fromthis point of view also the production process for the contact lensesaccording to the invention may be set up in an extremely economic way.

Opening of the mold so that the molded article can be removed from themold may take place in a manner known per se.

If the molded contact lens is produced solvent-free from an alreadypurified prepolymer according to the invention, then after removal ofthe molded lens, it is not normally necessary to follow up withpurification steps such as extraction. This is because the prepolymersemployed do not contain any undesired constituents of low molecularweight; consequently, the crosslinked product is also free orsubstantially free from such constituents and subsequent extraction canbe dispensed with. Accordingly, the contact lens can be directlytransformed in the usual way, by hydration, into a ready-to-use contactlens. Appropriate embodiments of hydration are known to the personskilled in the art, whereby ready-to-use contact lenses with very variedwater content may be obtained. The contact lens is expanded, forexample, in water, in an aqueous salt solution, especially an aqueoussalt solution having an osmolarity of about 200 to 450 milli-Osmole in1000 ml (unit: mOsm/ml), preferably about 250 to 350 mOsm/l andespecially about 300 mOsm/l, or in a mixture of water or an aqueous saltsolution with a physiologically compatible polar organic solvent, e.g.glycerol. Preference is given to expansions of the article in water orin aqueous salt solutions.

If the molded contact lens is produced from an aqueous solution of analready purified prepolymer according to the invention, then thecrosslinked product also does not contain any troublesome impurities. Itis therefore not necessary to carry out subsequent extraction. Sincecrosslinking is carried out in an essentially aqueous solution, it isadditionally unnecessary to carry out subsequent hydration. The contactlenses obtained by this process are therefore notable, according to anadvantageous embodiment, for the fact that they are suitable for theirintended usage without extraction. By intended usage is understood, inthis context, that the contact lenses can be used in the human eye.

Similarly, if the molded contact lens is produced from a solventsolution of an already purified prepolymer according to the invention,it is not necessary to carry out subsequent extraction, but instead ofhydration process to replace the solvent.

The molded contact lenses can be further subjected to further processes,such as, for example, surface treatment, sterilization, and the like.

A contact lens of the invention has an oxygen permeability of preferablyat least about 40 barrers, more preferably at least about 60 barrers,even more preferably at least about 80 barrers; and an elastic modulusof about 1.5 MPa or less, preferably about 1.2 MPa or less, morepreferably about 1.0 MPa or less. In accordance with the invention, anoxygen permeability is an apparent (directly measured when testing asample with a thickness of about 100 microns) oxygen permeabilityaccording to procedures described in Examples.

A contact lens of the invention further has an ion permeabilitycharacterized by having an Ionoflux Diffusion Coefficient, D, of,preferably at least about 1.5×10⁻⁶ mm²/min, more preferably at leastabout 2.6×10⁻⁶ mm²/min, even more preferably at least about 6.4×10⁻⁶mm²/min.

A contact lens of the invention further has a water content ofpreferably from about 15% to about 55%, more preferably from about 20%to about 38% by weight when fully hydrated. The water content of asilicone hydrogel contact lens can be measured according to BulkTechnique as disclosed in U.S. Pat. No. 5,849,811.

All of the various embodiments of the prepolymer described above can beused in this aspect of the invention.

In a further aspect, the invention provides a method for producing softcontact lenses. The method comprises the steps of: comprising the stepsof: providing a mold for making a soft contact lens, wherein the moldhas a first mold half with a first molding surface defining the anteriorsurface of a contact lens and a second mold half with a second moldingsurface defining the posterior surface of the contact lens, wherein saidfirst and second mold halves are configured to receive each other suchthat a cavity is formed between said first and second molding surfaces;introduce a lens-forming material into the cavity, wherein thelens-forming material comprises one or more actinically crosslinkableprepolymers and is substantially free of vinylic monomer and/orcrosslinking agent, wherein each of said one or more prepolymerscomprises (1) dangling polysiloxane units derived from one or moremonoethylenically functionalized polysiloxane-containing monomers and/orone or more monoethylenically-functionalized polysiloxane-containingmacromers, wherein the dangling polysiloxane units is free ofethylenically unsaturated groups, (2) hydrophilic units derived from oneor more hydrophilic vinylic monomers, (3) crosslinking units derivedfrom at least one polysiloxane-containing crosslinker and/or at leastone silicone-free crosslinker, (4) multiple ethylenically unsaturatedgroups, and (5) optionally hydrophobic units derived from at least onehydrophobic vinylic monomer; and actinically irradiating the compositionin the mold to crosslink said one or more crosslinkable prepolymers toform the contact lens.

All of the various embodiments of the prepolymer and contact lens of theinvention described above can be used in this aspect of the invention.

The previous disclosure will enable one having ordinary skill in the artto practice the invention. In order to better enable the reader tounderstand specific embodiments and the advantages thereof, reference tothe following examples is suggested.

EXAMPLE 1

Oxygen permeability measurements. The oxygen permeability of a lens andoxygen transmissibility of a lens material is determined according to atechnique similar to the one described in U.S. Pat. No. 5,760,100 and inan article by Winterton et al., (The Cornea: Transactions of the WorldCongress on the Cornea 111, H. D. Cavanagh Ed., Raven Press: New York1988, pp 273-280), both of which are herein incorporated by reference intheir entireties. Oxygen fluxes (J) are measured at 34° C. in a wet cell(i.e., gas streams are maintained at about 100% relative humidity) usinga Dk1000 instrument (available from Applied Design and Development Co.,Norcross, Ga.), or similar analytical instrument. An air stream, havinga known percentage of oxygen (e.g., 21%), is passed across one side ofthe lens at a rate of about 10 to 20 cm³/min., while a nitrogen streamis passed on the opposite side of the lens at a rate of about 10 to 20cm³/min. A sample is equilibrated in a test media (i.e., saline ordistilled water) at the prescribed test temperature for at least 30minutes prior to measurement but not more than 45 minutes. Any testmedia used as the overlayer is equilibrated at the prescribed testtemperature for at least 30 minutes prior to measurement but not morethan 45 minutes. The stir motor's speed is set to 1200±50 rpm,corresponding to an indicated setting of 400±15 on the stepper motorcontroller. The barometric pressure surrounding the system,P_(measured), is measured. The thickness (t) of the lens in the areabeing exposed for testing is determined by measuring about 10 locationswith a Mitotoya micrometer VL-50, or similar instrument, and averagingthe measurements. The oxygen concentration in the nitrogen stream (i.e.,oxygen which diffuses through the lens) is measured using the DK1000instrument. The apparent oxygen permeability of the lens material,Dk_(app), is determined from the following formula:Dk _(app) =Jt/(P _(oxygen))where J=oxygen flux [microliters O₂/cm²-minute]

P_(oxygen)=(P_(measured)−P_(water) vapor)=(% O₂ in air stream) [mmHg]=partial pressure of oxygen in the air stream

P_(measured)=barometric pressure (mm Hg)

P_(water) vapor=0 mm Hg at 34° C. (in a dry cell) (mm Hg)

P_(water) vapor=40 mm Hg at 34° C. (in a wet cell) (mm Hg)

t=average thickness of the lens over the exposed test area (mm)

where Dk_(app) is expressed in units of barrers. The oxygentransmissibility (Dk/t) of the material may be calculated by dividingthe oxygen permeability (Dk_(app)) by the average thickness (t) of thelens.

Ion Permeability Measurements. The ion permeability of a lens ismeasured according to procedures described in U.S. Pat. No. 5,760,100(herein incorporated by reference in its entirety. The values of ionpermeability reported in the following examples are relative ionofluxdiffusion coefficients (D/D_(ref)) in reference to a lens material,Alsacon, as reference material. Alsacon has an ionoflux diffusioncoefficient of 0.314×10⁻³ mm²/minute.

EXAMPLE 2

Preparation of Initiator Solution

Initiator solutions are prepared by dissolving a desired amount of aninitiator in t-amyl alcohol as shown in Table 1. The resulting solutionis stirred and degassed at room temperature 2 times for 5 minutes eachbelow 50 mbar.

TABLE 1 Reactant/Example 2a (grams) 2b (grams) AIBN 0.059 0.059 t-amylalcohol 11.40 11.44Preparation of Reactor Solution

Various reactants shown in Table 2 are weighed into a 500 mL reactorequipped with vacuum and nitrogen. The resulting solution is stirred andchilled to 4° C. and then degassed 10 times for 5 minutes each at lessthan 1 mbar, using nitrogen to back-fill.

TABLE 2 Example Reactant 2a (grams) 2b (grams) PDMS-11500 diacrylamide11.50 8.05 PDMS-5000 monomethacrylate “MCR-M17”* NA 3.45 Aminopropylmethacrylate hydrochloride 1.33 1.33 Acrylic Acid 0.04 0.04 Hydroxyethylacrylate 5.30 5.30 N,N-dimethylacrylamide 7.96 7.96 t-amyl alcohol320.42 320.35 *from GelestPreparation of Prepolymer

A reactor solution temperature prepared above is rapidly raised to 68°C. At this temperature, an initiator solution is injected in whiletaking care to exclude oxygen from the system. This system is allowed toreact for 5 hours when the temperature is rapidly reduced to roomtemperature.

The cooled reaction solution is filtered through a Por 3 fritted Buchnerfunnel with 1-propanol rinsing. To the filtered solution, 0.016 ghydroxyl-TEMPO is added. The solution is rotovapped at 45° C. and 80-100mbar to remove the alcohols in three steps, each time replacing theremoved alcohol with deionized water until less than ˜5% solventremained. This process results in an emulsion.

70% of this emulsion is taken for the acrylation step as follows. Theemulsion is chilled to 0° C. and the pH is adjusted to 9.5 using NaOH. Atotal of 580 μL of acryloyl chloride (96% pure) is added in twoadditions of 290 μL each. The solution is warmed to at least 10° C. whenit is neutralized to pH7 using 2N HCl. This emulsion is filtered througha Por3 fritted Buchner. It is then ultra-filtered using a Millipore PLGC10K regenerated cellulose cartridge until the permeate has aconductivity less than 3 μS/cm. It is concentrated slightly to ˜1%solids in water on the ultrafiltration unit and then freeze-dried. Thepowder resulting from this process is termed a prepolymer.

Preparation of Silicone Hydrogel Contact Lenses

A lens formulation is prepared from a prepolymer prepared above bymixing 65% prepolymer with 0.16% Irgacur 2959 (relative to totalformulation) and 34.84% 1-propanol. After dissolution, the formulationis dosed into PP molds, cured under a Hamamatsu lamp at 4 mW/cm² forabout 44 seconds (Example 2a) and about 60 seconds (Example 2b)respectively.

The resulting lenses are demolded using water at room temperature.Lenses are not extracted. Lenses are autoclaved for 30 minutes at 121°C. in phosphate buffered saline. Lens properties are determined andreported in Table 3. It is found that by substituting about 3.45% ofpolysiloxane crosslinker with a monomethacrylate PDMS (for forming aprepolymer with dangling polysiloxane polymer chains), the resultantlenses have a reduction in modulus of about 44%

$\left( {\frac{1.33 - 0.75}{1.33} \times 100\%} \right),$an increase in IP of about 109%

$\left( {\frac{18 - 8.6}{8.6} \times 100\%} \right),$and substantially unchanged oxygen permeability (Dk).

TABLE 3 NVE, % water Dk* Modulus average diameter Example residualcontent (%) (barrer) E′ (MPa) ETB % (mm) IP^(#) 2a 7.6 36 88 1.33 15813.8 8.6 2b 11.5 38 89 0.75 157 14.2 18 NVE: non-volatile extractable;*apparent Dk; ETB: elongation at break; ^(#)ion permeability relative toAlsacon.

1. A soft contact lens, comprising: a silicone hydrogel material that isobtained by curing a lens-forming material in a mold, wherein thelens-forming material comprises at least one actinically crosslinkableprepolymer and is substantially free of vinylic monomers andcrosslinking agent with molecular weight of less than 1500 dalton,wherein the prepolymer comprises (1) dangling polysiloxane units derivedfrom one or more monoethylenically functionalizedpolysiloxane-containing monomers and/or one or moremonoethylenically-functionalized polysiloxane-containing macromers,wherein the dangling polysiloxane units is free of ethylenicallyunsaturated groups; (2) hydrophilic units derived from one or morehydrophilic vinylic monomers; (3) crosslinking units derived from atleast one polysiloxane-containing crosslinker which comprises two ormore ethylenically unsaturated groups and a moiety of

in which R₁ and R₂ are independently a monovalent C₁-C₁₀ alkyl, C₁-C₁₀ether, C₁-C₁₀ fluoroalkyl, C₁-C₁₀ fluoroether, or C₆-C₁₈ aryl radical,which may comprise hydroxy group, primary, secondary, or tertiary aminegroup, carboxy group, or carboxylic acid; n is an integer of 4 orhigher; (4) multiple ethylenically unsaturated groups; and (5)optionally hydrophobic units derived from at least one hydrophobicvinylic monomer.
 2. The contact lens of claim 1, wherein the softcontact lens has at least one of lens property selected from the groupconsisting of: an elastic modulus of about 1.2 MPa or less; an oxygenpermeability of at least about 40 barrers; an Ionoflux DiffusionCoefficient, D, of at least about 1.5×10⁻⁶ mm²/min; a water content offrom about 15% to about 55% when fully hydrated, and a combinationthereof.
 3. The contact lens of claim 2, wherein the at least oneactinically crosslinkable prepolymer is previously purified byprecipitation with organic solvents, filtration and washing, extractionin a suitable solvent, dialysis, or ultrafiltration.
 4. The contact lensof claim 2, wherein the dangling polysiloxane units is present in theprepolymer in an amount sufficient to provide the contact lens with areduction in modulus of at least about 10% or more and/or with anincrease in ion permeability of at least about 20% or more.
 5. Thecontact lens of claim 4, wherein the intermediary copolymer is obtainedby copolymerization of an actinically polymerizable composition A or B,wherein the composition A comprises the components of: (1) at least onemonoethylenically functionalized polysiloxane-containing monomer and/orat least one monoethylenically unsaturated polysiloxane-containingmacromer, (2) at least one hydrophilic vinylic monomer, (3) at least onepolysiloxane-containing crosslinker, and (4) optionally at least onehydrophobic vinylic monomer, provided that at least one of components(2)-(4) further comprises at least one functional group through which anethylenically unsaturated group can be covalently linked to the obtainedintermediary copolymer, wherein the composition B comprises thecomponents of: (1) at least one monoethylenically functionalizedpolysiloxane-containing monomer and/or at least one monoethylenicallyunsaturated polysiloxane-containing macromer, (2) at least onehydrophilic vinylic monomer, (3) at least one polysiloxane-containingcrosslinker, (4) optionally at least one hydrophobic vinylic monomer,and (5) at least one chain transfer agent having a functional groupthrough which an ethylenically unsaturated group can be covalentlylinked to the obtained intermediary copolymer.
 6. The contact lens ofclaim 5, wherein the at least one monoethylenically functionalizedpolysiloxane-containing monomer and the at least one monoethylenicallyunsaturated polysiloxane-containing macromer independently of each otherare defined by

in which X denotes —COO—, —CONR₁₄—, —OCOO—, or —OCONR₁₄—, where each R₁₄is independently H or C₁-C₇ alkyl; R₁₁ denotes a divalent C₁-C₂₅ alkylor C₆ -C₃₀ aryl radical, which may interrupted by —O—, —COO—, —CONR₁₄—,—OCOO— or —OCONR₁₄— and may comprise hydroxy group, primary, secondary,or tertiary amine group, carboxy group, or carboxylic acid; R₁₂ is amonovalent C₁-C₂₅ alkyl or C₆-C₃₀ aryl radical, which may interrupted by—O—, —COO—, —CONR₁₄—, —OCOO— or —OCONR₁₄— and may comprise hydroxygroup, primary, secondary, or tertiary amine group, carboxy group, orcarboxylic acid; R₃, R₄, R₅′, R₆, R₇, R₈, R₉ and R₁₀, independently ofone another, are C₁-C₈-alkyl, C₁-C₄ alkyl- or C₁-C₄- alkoxy-substitutedphenyl, fluoro(C₁-C₁₈-alkyl), cyano(C₁-C₁₂-alkyl), hydroxy-C₁-C₆-alkylor amino-C₁-C₆-alkyl; m and p independently of each other are an integerof from 5 to 700 and (m+p) is from 5 to
 700. 7. The contact lens ofclaim 6, wherein the at least one hydrophilic vinylic monomer isselected from the group consisting of N,N-dimethylacrylamide (DMA),2-hydroxyethylmethacrylate (HEMA), 2-hydroxyethyl acrylate (HEA),hydroxypropyl acrylate, hydroxypropyl methacrylate (HPMA),trimethylammonium 2-hydroxy propylmethacrylate hydrochloride,Aminopropyl methacrylate hydrochloride, dimethylaminoethyl methacrylate(DMAEMA), glycerol methacrylate (GMA), N-vinyl-2-pyrrolidone (NVP),dimethylaminoethylmethacrylamide, acrylamide, methacrylamide, allylalcohol, vinylpyridine, N-(1,1dimethyl-3-oxobutyl)acrylamide, acrylicacid, a C₁-C₄-alkoxy polyethylene glycol (meth)acrylate having a weightaverage molecular weight of from 200 to 1500, methacrylic acid, N-vinylformamide, N-vinyl acetamide, N-vinyl isopropylamide, N-vinyl-N-methylacetamide, allyl alcohol, N-vinyl caprolactam, and combinations thereof.8. The contact lens of claim 7, wherein the polymerizable composition Aor B further comprises at least one silicone-containing vinylic monomerselected from the group consisting of 3-methacryloxypropylpentamethyldisiloxane,bis(methacryloxypropyl)-tetramethyldisiloxane,N-[tris(trimethylsiloxy)silylpropyl]-acrylamide,N-[tris(trimethylsiloxy)silylpropyl]methacrylamide, andtris(trimethylsilyloxy)silylpropyl-methacrylate,N-[tris(trimethylsiloxy)silylpropyl]methacrylamide,N-[tris(trimethylsiloxy)silylpropyl]acrylamide,(3-methacryloxy-2-hydroxypropyloxy)-propylbis(trimethylsiloxy)methylsilane,(3-methacryloxy-2-hydroxypropyloxy)propyl -tris(trimethylsiloxy)silane,(3-methacryloxy-2-(2-hydroxyethoxy)propyloxy)propyl-bis(trimethylsiloxy)methylsilane,N-2-methacryloxyethyl-O-(methyl-bis-trimethylsiloxy-3-propyl)silylcarbamate,1,3-bis[4-vinyloxycarbonyloxy)but-1-yl]tetramethyl-disiloxane,3-(trimethylsilyl)propyl vinyl carbonate,3-(vinyloxycarbonylthio)propyl-[tris(trimethyl -siloxy)silane],3-[tris(trimethylsiloxy)silyl]propylvinyl carbamate,3-[tris(trimethylsiloxy)silyl]propyl allyl carbamate,3-[tris(trimethylsiloxy)silyl]propyl vinyl carbonate,t-butyldimethylsiloxyethyl vinyl carbonate, trimethylsilylethyl vinylcarbonate, trimethylsilylmethyl vinyl carbonate, and combinationsthereof.
 9. The contact lens of claim 8, wherein intermediary copolymercomprises: (1) from about 5% to about 40% by weight of danglingpolysiloxane units derived from one or more monoethylenicallyfunctionalized polysiloxane-containing monomers and/or macromers; (2)from about 20% to about 60% by weight of hydrophilic units derived fromone or more hydrophilic monomers; (3) from about 1% to about 60% byweight of crosslinking polysiloxane units derived from apolysiloxane-containing crosslinker; (4) from 0 to about 2% by weight ofsilicone-free crosslinker; and (5) from 1% to about 30% by weight ofsilicone-containing units derived from one or more silicone-containingvinylic monomers.